无定形氧卤化物固态导体中碱金属离子传输机制
Mechanisms of alkali ionic transport in amorphous oxyhalides solid state conductors
AI总结：
研究揭示无定形氧卤化物中碱金属离子传输机制，通过分子动力学分析发现氧阴离子限制碱金属扩散，且传输特性对原子化学变化不敏感。
摘要：
无定形氧卤化物因其相对较高的离子导电性（>1 mS cm⁻¹）、优异的化学稳定性、机械柔软性和通过标准固态反应简便的合成路线而受到广泛关注。这些材料表现出几乎不依赖于底层化学的离子导电性，这与晶体导体的情况形成鲜明对比。在本工作中，我们采用精确调优的机器学习原子间势能函数，构建涵盖数百纳秒的分子动力学轨迹，以获得统计收敛的传输特性。我们发现无定形状态由各种长度的金属-阴离子四面体链片段组成。通过分析碱金属阳离子围绕四面体协调的三价金属离子迁移的停留时间，我们发现金属-阴离子四面体上的氧阴离子限制了碱金属的扩散。通过计算离子导电性的完整爱因斯坦表达式，我们证明这些材料的碱金属传输数受到不同粒子相关性的影响，同时它们的碱金属海文比接近于一，表明离子传输主要由不相关的自扩散决定。最后，通过将此分析扩展到化学组成AMX₂.₅O₀.₇₅，涵盖不同的碱性（A = Li，Na，K）、金属（M = Al，Ga，In）和卤素（X = Cl，Br，I）物种，我们阐明了为何这些材料的扩散特性对原子化学的变化几乎不敏感。
英文摘要：
Amorphous oxyhalides have attracted significant attention due to their relatively high ionic conductivity ($>$1 mS cm$^{-1}$), excellent chemical stability, mechanical softness, and facile synthesis routes via standard solid-state reactions. These materials exhibit an ionic conductivity that is almost independent of the underlying chemistry, in stark contrast to what occurs in crystalline conductors. In this work, we employ an accurately fine-tuned machine learning interatomic potential to construct large-scale molecular dynamics trajectories encompassing hundreds of nanoseconds to obtain statistically converged transport properties. We find that the amorphous state consists of chain fragments of metal-anion tetrahedra of various lenght. By analyzing the residence time of alkali cations migrating around tetrahedrally-coordinated trivalent metal ions, we find that oxygen anions on the metal-anion tetrahedra limit alkali diffusion. By computing the full Einstein expression of the ionic conductivity, we demonstrate that the alkali transference number of these materials is strongly influenced by distinct-particles correlations, while at the same time they are characterized by an alkali Haven ratio close to one, implying that ionic transport is largely dictated by uncorrelated self-diffusion. Finally, by extending this analysis to chemical compositions $AMX_{2.5}\textsf{O}_{0.75}$, spanning different alkaline ($A$ = Li, Na, K), metallic ($M$ = Al, Ga, In), and halogen ($X$ = Cl, Br, I) species, we clarify why the diffusion properties of these materials remain largely insensitive to variations in atomic chemistry.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
